(PARI) lista(nn) = {forstep(n=1, nn, 2, if (bigomega(n) % 2 == 0, print1(n, ", "))); } \\
Michel Marcus, Jul 04 2015
(Python)
from math import isqrt, prod
from sympy import primerange, integer_nthroot, primepi
from oeis_sequences.OEISsequences import bisection
if n==1: return 1
def g(x, a, b, c, m): yield from (((d, ) for d in enumerate(primerange(b, isqrt(x//c)+1), a)) if m==2 else (((a2, b2), )+d for a2, b2 in enumerate(primerange(b, integer_nthroot(x//c, m)[0]+1), a) for d in g(x, a2, b2, c*b2, m-1)))
def f(x): return int(n+x-2-sum(sum(primepi(x//prod(c[1] for c in a))-a[-1][0] for a in g(x, 0, 1, 1, m)) for m in range(2, x.bit_length()+1, 2))+(y:=x>>1)-sum(sum(primepi(y//prod(c[1] for c in a))-a[-1][0] for a in g(y, 0, 1, 1, m)) for m in range(2, x.bit_length(), 2)))
